There exist a large number of theories for dark matter; however, gauge theories can be very appealing due to the fact that the dark matter properties can be defined by a new gauge symmetry in nature. Then, it is possible to have different extensions of the Standard Model where one of the SM global symmetries is promoted to a local symmetry.
For example, if we add three copies of right-handed neutrinos it is possible to have a theory based on local \(B\!-\!L\) . In this context, it is not possible to predict
the existence of a dark matter candidate but extra fields are required to play this role, see for example the study in Ref. [1]}.
The existence of a fermionic dark matter can be predicted in gauge theories when one of the fields needed for anomaly cancellation is in fact stable and has the right properties to describe the cold dark matter in the Universe.
At the same time, the stability of the dark matter
candidate can be a consequence of the new gauge symmetry breaking mechanism. The simplest theories we know where one can realize this
idea are based on local baryon and lepton numbers [2]}, [3]}, for a recent review see [4]}. The theories based on local baryon number could describe physics at the scale very close to the electroweak scale, and therefore, there is hope to test them in the near future.
